Ryan's been DOMINANT -- he ran through the promotion's HW tournament, beating guys like Matt Mitrione and the legendary Fedor Emelianenko ... prompting Bellator honcho Scott Coker to declare Bader "the best heavyweight fighter on the planet."

Guess what? Bader says his boss is right!!!

"I went through that tournament, I didn't get punched in the face one time," Bader tells us. "Why shouldn't I believe that? I believe I can beat anyone at any given time and that includes heavyweights."

"So, I don't think that's a crazy statement. You put myself and Stipe or Cormier in there, I do believe I can beat them."

Bader says he's hopeful that the future may hold some cross-promotional dream fight that'd pair him against the UFC's top big guys ... but before that, he's gotta deal with 6'4, 235lb. Kongo who was a part of one of MMA's craziest fights ever.